Sonophotocatalytic treatment of wastewater using simulated solar light-driven Bi2O3-ZnO nanophotocatalyst sensitized with copper phthalocyanine

Abstract

Bi2O3–ZnO photocatalysts with various amounts of copper phthalocyanine (CuPc) as photosensitizer agent were synthesized and used as novel photocatalysts in sonophotocatalytic degradation of methyl orange (MO). The sonophotocatalytic degradation of MO under simulated solar light irradiation was compared with sole photocatalysis and sole sonolysis, and the results showed that the decomposition performance was in the following order: sonophotocatalysis (30 W ultrasonic power) > photocatalysis > sonophotocatalysis (60 W ultrasonic power) > sonolysis. Among CuPc-Bi2O3–ZnO sonophotocatalysts with different contents of CuPc from 0% to 2% wt., the sample with 2% wt. indicated the highest MO sonophotodegradation percent of 94.66%. The characterization properties of synthesized sonophotocatalysts were identified by XRD, FESEM/EDX, BET/BJH, FTIR, TEM, and UV–Vis DRS. The XRD patterns indicated that, with increasing the CuPc amount from 0% to 2% wt., the crystallite size of ZnO in studied photocatalysts decreased from 54 to 41 nm. However, FESEM analysis illustrated fine nanoparticles (15–25 nm) with agglomeration on the outer surface that are related to Bi2O3 and CuPc particles. UV–Vis DRS showed that the sample with 2% wt. of CuPc had the highest visible light absorption and the lowest bandgap energy of 2.63 eV. The highest surface area and the smallest pore size were observed in this sample as well. The reusability test exhibited the excellent stability of CuPc-Bi2O3–ZnO sonophotocatalyst within six consecutive runs with negligible (5%) fading in sonophotocatalytic performance. Scavenger tests indicated that OH radical was not the dominant reactive specie, and sonication via physical aspects and production of other radicals influenced the photocatalytic reaction.